The Aero Precision PRO 5.56 Bolt Carrier Group is built from the ground up to meet the demands of the most extreme conditions. Each component and manufacturing process of the PRO 5.56 Bolt Carrier Group was deliberately chosen to increase the reliable service life of the bolt carrier group and its components.

Bolt

The bolt is one of the most important parts of the bolt carrier group. Machined from 9310 steel, a proprietary flash nitride process was chosen to ensure proper heat treatment on the bolt. When properly heat treated, 9310 steel provides superior strength and durability when compared to C158.

The cam pin channel is counter bored, eliminating the need for swaging. Swaging is the industry standard, however this process creates more stress on the bolt during manufacturing by displacing material rather than cutting it to the proper dimension from the start.

• Machined from 9310 steel
• Shot peened
• MPI tested
• Proper heat treatment ensured via proprietary flash-nitriding process

Cam Pin

Each PRO cam pin is precision ground after heat treatment to exacting specifications and given a nitride finish.

The cam pin features an engraved indexing mark on one side of the cam pin face; a concept that has been popularized by Chad Albrecht at School of the American Rifle. Cam pins traditionally wear more heavily on one side and when installed inconsistently can create excessive wear over time. When the cam pin becomes “loose” this can create excessive wear on the bolt itself shortening overall life. The indexing mark allows for consistent installation during maintenance which in turn reduces wear on not only the cam pin but the bolt over time to help extend overall service life.

• Machined from 4140 steel
• Precision ground after heat treatment
• Engraved indexing mark
• Nitride finish

Extractor

The extractor features a phosphate finish. The extractor is one of the few places where it is beneficial to have a “rougher” finish as it allows for more positive engagement with the case when pulling it out of the chamber.

• Machined from 4140 steel
• Heat treated
• Shot peened
• Phosphate finish

Carrier

Each PRO BCG utilizes a M16 cut carrier and features a nitride finish. Internal critical surfaces are precision ground to exacting tolerances to ensure optimal gas efficiency. The same machining standards are used for the carrier rails providing a super smooth fit and function from the start.

• Machined from 8620 steel
• M16 Cut Carrier
• Nitride Finish
• Critical surfaces precision ground for optimal gas efficiency and reliability

Gas Key

• Machined from hardened 4140 steel
• Torqued to spec with grade 8 hex fasteners
• Properly staked to mil-spec
• Nitride finish

Ejector

• Machined from S7 tool steel

Firing Pin

• Ground from 8640 steel
• Nitride Finish